As a next-generation communication system of the W-CDMA (Wideband Code Division Multiple Access) system or the HSDPA (High Speed Downlink Packet Access) system (collectively called UMTS (Universal Mobile Telecommunications System)), an LTE (Long Term Evolution) system has been studied by 3GPP (3rd Generation Partnership Project) which is a standards body of the UMTS. More specifically, in the LTE system as a radio access system, an OFDM (Orthogonal Frequency Division Multiplexing) scheme and an SC-FDMA (Single-Carrier Frequency Division Multiple Access) scheme have been studied to be applied to the downlink communications system and the uplink communications system, respectively (see, for example, 3GPP TR 25.814 (V7.0.0), “Physical Layer Aspects for Evolved UTRA,” June 2006).
A base station apparatus broadcasts broadcast information items (hereinafter may be referred to as broadcast information) indicating such as a configuration of a common channel, restriction information, measurement control information, neighboring cell information and the like using a Broadcast Control Channel (BCCH). Further, there may arise necessity for changing the contents of the broadcast information. For example, if congestion in the network is detected, the contents of the restriction information may be changed (updated); and if a new cell is added to coverage cells of the base station apparatus, the neighboring cell information may be changed. Further, an initial transmission power value of a Random Access Channel (RACH) may vary depending on a measured uplink interference amount.
In order to change the contents of the broadcast information, the changed contents of the broadcast information are required to be reported to user equipment (hereinafter referred to as a user equipment (UE) terminal(s)). In this case, for example, a signaling such as a Paging Channel (PCH) may be reported through a network to the base station apparatus; then, the base station apparatus reports that the broadcast information has been changed to a user equipment (UE) terminal by signaling. This signaling is called Broadcast Control Channel Change Notification (BCCH Change Notification) or System Information Change Notification. Upon receiving the BCCH Change Notification from the base station apparatus, the user equipment (UE) terminal performs a re-reception process of the changed broadcast information.
While waiting for an incoming call, i.e., in an idle (RRC_IDLE) mode, a user equipment (UE) terminal monitors the Paging Channel (PCH) at a predetermined timing assigned to a group to which the user equipment (UE) belongs. In other words, reception timings of the paging differ depending on the groups to which the user equipment (UE) terminals belong. When there is an incoming call to a user equipment (UE) terminal belonging to a group, the base station apparatus transmits signaling using a Paging-Radio Network Temporary Identity (P-RNTI) in a Physical Downlink Control Channel (PDCCH). The Physical Downlink Control Channel (PDCCH) includes information items indicating positions of resource blocks for a Physical Downlink Shared Channel (PDSCH), Transport Block format (TB format) and the like. The Physical Downlink Control Channel (PDCCH) may also be called an L1/L2 Control Channel (L1/L2 CCH). Specifically, the Physical Downlink Shared Channel (PDSCH) includes the user equipment identity (UE ID) of the paging user equipment (UE) terminal.
As shown in FIG. 1, the user equipment (UE) terminal checks (determines) whether there is the Physical Downlink Control Channel (PDCCH) addressed to the P-RTNI at a Discontinuous Reception (DRX) timing of the user equipment (UE) terminal. When determining that there is the Physical Downlink Control Channel (PDCCH) addressed to the P-RTNI, the user equipment (UE) terminal further receives the Physical Downlink Shared Channel (PDSCH) to determine whether there is the user equipment identity (UE ID) of the user equipment (UE) terminal in the received Physical Downlink Shared Channel (PDSCH); and when determining that there is the user equipment identity (UE ID) of the user equipment (UE) terminal, the user equipment (UE) terminal determines that there is an incoming call to the user equipment (UE) terminal and starts a connection procedure.
On the other hand, when there is no paging user equipment (UE) terminal, neither the Physical Downlink Control Channel (PDCCH) nor the Physical Downlink Shared Channel (PDSCH) is transmitted and the resources for those channels may be used for data transmission and the like.
When a user equipment (UE) terminal performs a cell re-selection and moves into a new cell to wait for an incoming call in the new cell, the user equipment (UE) terminal always receives all broadcast information in the new cell. Therefore, as long as the broadcast information has been changed before the user equipment (UE) terminal moves into a new cell, the user equipment (UE) terminal always receives all broadcast information in the new cell, and the change of the broadcast information is reflected. On the other hand, however, in a case where the broadcast information is changed while a user equipment (UE) terminal is waiting for an incoming call, the user equipment (UE) terminal cannot recognize the change of the broadcast information unless (1) the change of the broadcast information is reported to the user equipment (UE) terminal or (2) the user equipment (UE) terminal periodically performs the re-reception processes of the broadcast information (e.g., unless the user equipment (UE) terminal recognizes a broadcasted Value Tag). From the viewpoint of saving battery power, the former case (1) is preferable rather than the latter case (2) because in the latter case (2), the battery of the user equipment (UE) terminal is wasted by periodically performing the re-reception processes. A user equipment (UE) terminal performs a reception process to receive paging data at predetermined timings for paging only. Because of this feature, from the viewpoint of saving battery power, it is preferable that the change of the broadcast information is notified at the predetermined timing for paging.
Due to the above mentioned features, as a method of notifying the change of the broadcast information to the user equipment (UE) terminal, the following methods (1) through (4) have been proposed (see, for example, 3GPP R2-073235, August 2007, and 3GPP R2-073304, August 2007).
(1): A method of transmitting the Physical Downlink Control Channel (PDCCH) to the P-RNTI so that the BCCH Change Notification is performed by using the Physical Downlink Control Channel (PDCCH).
(2): A method of transmitting the Physical Downlink Control Channel (PDCCH) to the P-RNTI so that the BCCH Change Notification is performed by using the Physical Downlink Shared Channel (PDSCH) addressed by the Physical Downlink Control Channel (PDCCH).
(3): A method of transmitting the Physical Downlink Control Channel (PDCCH) to a Broadcast Control Channel-change-Radio Network Temporary ID (BCCH-change-RNTI) so that the BCCH Change Notification is performed by using the Physical Downlink Control Channel (PDCCH).
(4): A method of transmitting the Physical Downlink Control Channel (PDCCH) to the Broadcast Control Channel-change-Radio Network Temporary ID (BCCH-change-RNTI) so that the BCCH Change Notification is performed by using the Physical Downlink Shared Channel (PDSCH) addressed by the Physical Downlink Control Channel (PDCCH).
In any of the above methods, the change of the broadcast information is required to be notified to all the user equipment (UE) terminals waiting in the cell. Therefore, the signaling (i.e., the BCCH Change Notification) is repeatedly transmitted. For example, by considering the possibility that a user equipment (UE) terminal fails to receive the signaling, the signaling is required to be repeatedly notified during a period about two or three times longer than a Discontinuous Reception (DRX) cycle.